More heavy precipitation in the forecast is keeping avalanche danger high.
Confidence
Fair - Forecast snowfall amounts are uncertain
Weather Forecast
Wednesday night and Thursday: Another wave associated with the frontal system should bring some good precipitation quantities (10-20 mm until Thursday evening) and with strong W winds easing off a bit Thursday but staying in the moderate to strong speeds. Freezing levels rising close to 2000 m.Friday: Precipitation should start tapering off as the westerly flow weakens. Temperatures and freezing level are expected to lower slightly. Winds should to remain in the moderate to strong from the W. Saturday: A little bit more precipitation is expected but no significant amounts. Light SW winds and freezing levels starting to drop significantly to reach 800 m. by the end of the period.
Avalanche Summary
2 size 2 slab avalanches were reported which would have slid on the older (pre-storm) snow surface. I suspect lots more natural avalanche activity today especially where there was significant amounts of precipitation.
Snowpack Summary
The warm storm has already added a significant load onto the snowpack (around 30 mm of water equivalent in the higher snowfall areas). Another pulse of precipitation will add weight onto the storm slab and the already moist/wet snowpack below the freezing line (around 2000 m.). In the alpine and at treeline, the new snow will sit on a 2 cm thick suncrust on SE-S-SW facing slopes, some buried windslabs and possibly some well developed surface hoar on shaded slopes. At lower elevations, the wet precipitation will keep soaking up the snowpack possibly weakening it especially where there is a good buried sliding surface like a crust or a surface hoar layer. The surface hoar layer buried down 100 cm is still a concern and would generate a very large avalanche if triggered.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.